fix(web): improve DSL export feedback

[lyzno1]

Summary

• render Base UI promise toast loading states with the Dify spinner treatment
• split direct app DSL export from the Workflow and Advanced Chat secret preflight using generated contracts
• expose one mutation lifecycle across preflight and export, and surface pending feedback in App cards, the app sidebar, and Agent v2
• keep App card action menus consistently sized without coupling tests to CSS

Why

DSL exports could appear idle while requests were pending. Workflow callers also fetched the full draft only to inspect secret environment variables, while Agent v2 does not use workflow drafts.

User impact

Users now get immediate loading feedback and duplicate export requests are prevented. Workflow exports only read the smaller environment-variable endpoint before deciding whether secret confirmation is required.

Validation

• cd web && vp test run app/components/app/__tests__/use-export-app-dsl.spec.tsx app/components/apps/__tests__/app-card.spec.tsx app/components/app-sidebar/app-info/__tests__/use-app-info-actions.spec.ts app/components/app-sidebar/app-info/__tests__/app-info-detail-panel.spec.tsx app/components/app-sidebar/app-info/__tests__/app-info-modals.spec.tsx features/agent-v2/roster/components/__tests__/agent-roster-list.spec.tsx features/agent-v2/agent-detail/__tests__/navigation.spec.tsx app/components/workflow/__tests__/dsl-export-confirm-modal.spec.tsx
• cd web && pnpm type-check
• cd packages/dify-ui && vp test run --project unit src/toast/__tests__/index.spec.tsx
• cd packages/dify-ui && vp test --project storybook --run src/toast/index.stories.tsx
• cd packages/dify-ui && pnpm type-check
• git diff --check